The focus of this study is the inter-tidal sediment and eroding woody peat exposed in Clachan Harbour, Isle of Raasay, in the Scottish Inner Hebrides. These deposits were investigated as part of a wider project to monitor the impact of a new harbour and infrastructure works. Previous surveys of the harbour recorded the extent of the eroding peat along with borehole investigations and diatom analysis. Further excavation work supported by a programme of radiocarbon dating has raised the significance of the site, particularly in the light of Mesolithic worked stone tools which were found at the head of the harbour. Important sea-level data has been attained through altitudinal levelling thus allowing the site to be placed in its local and regional context.